A research program designed to study the collagen-mineral interface in dentin is proposed. Particular attention will be focused on the chemical properties of dentin collagen responsible for its interaction with crystalline hydroxylapatite by comparative studies of predentin collagen and age related experiments using bone and skin collagen. The influence of dentin phosphoprotein on this interaction will also be ascertained. Identically isolated and purified collagen components from dentin, bone, and skin will be studied by affinity chromatographic techniques on 100% crystalline calcium hydroxylapatite, phosphoprotein-bound hydroxylapatite, and native bone mineral. Chromatographic behavior will be related to chemical properties of tissue and age specific origin. In this way, the in vivo significance of the chromatography studies will be investigated. Specifically proposed as a working hypothesis is the interaction of collagen bound galactose with the crystalline component of hard tissue, this carbohydrate moiety serving possibly to regulate the amorphous to crystalline conversion during normal calcification. Investigations of the degree of mineral crystallinity in excised hard tissues, as well as, in vitro mineralization studies will parallel chemical analyses of hydroxylysine glycosylation and chromatographic behavior on affinity columns. A detailed comparison of the neutral carbohydrate distributions in dentin, bone, and skin collagens will be essential to the program.